ROCs is an acronym for Renewable Obligation Certificates. They are issued to 'green' energy producers based on the number of kilowatt hours generated. The fossil fuelled generators needs to acquire ROCs to the value of a percentage of the engergy they produce (currently set at 3% of their energy output).

Whilst small proudcers are unable to auction their ROCs, by amalgamating them into larger volumes, they can be auctioned the the NFPA on-line auction.